1. Field of the Invention
Embodiments of the present invention generally relate to data storage and, more particularly, to a method, system, and computer program product for maintaining the order of write-commands issued to a data storage.
2. Description of the Related Art
In information sharing and processing environments, many businesses employ data processing systems for storing and processing data. Often, the viability of a business depends on the reliability of access to data storage contained within its data processing system. As such, businesses seek reliable and efficient ways to consistently protect their data processing systems and the data storage contained therein from natural disasters, acts of terrorism, and unauthorized access, or computer hardware and/or software failures. Remote backup systems have been used for the protection of data storage by minimizing or eliminating loss of data, thereby forming an important aspect of business strategy and a key element in information sharing and processing environments. A duplicate of the data volume is prepared by transferring the data (hereinafter referred as replication) written in one information processing system to one remote backup system in a remote location. A technique to asynchronously transfer duplicate data is known as asynchronous replication.
In asynchronous replication, a host computer (host) may request a write operation at a first time; however, the data processing system performs data transfer to the remote backup at a second time that is after returning to a host a response indicating the backup is complete. Hence, write-commands from the host may not be sent to the remote backup until a later time. The downside of this technique is that the possibility of data loss if the data has not been stored onto both the data storage and the remote backup when a fault occurs. When a duster of multiple hosts share the data storage that is asynchronously replicated to the remote backup, co-ordination across the multiple hosts is necessary in order to ensure that the write-commands are applied to the remote backup in the exact same order as they have been applied at the data storage.
One of the ways to ensure order of the write-commands in the remote backup is by assigning a global time-stamp to each write-command issued by one or more hosts of the clustered environment. However, most of the known replication data processing models require complex co-ordination in a parallel clustered environment to assign such a time stamp and generate an ordered stream of write-commands. Such co-ordination across hosts requires network messages be communicated amongst host computers and can degrade performance of clustered applications.
Therefore, there is a need in the art for method, apparatus and computer program product to maintain the order of write-commands issued by one or more hosts of the clustered applications without substantially affecting performance of the clustered applications.